1. Field of the Invention
This invention relates to a method and device for measuring metals in a fluid stream, and more specifically, this invention relates to a method and device for simultaneously measuring metals in a gas stream while also providing archival samples.
2. Background of the Invention
The problems associated with the presence of metal particulates in air due to combustion and other activities continue to increase. As a result, the U.S. Environmental Protection Agency requires analysis of a number of metals in gas streams from combustors, incinerators, and other such entities.
Also, many industrial processes depend on the analysis of process streams before and/or after certain operations.
Present sampling techniques include manual stack sampling, which involves wet chemical analysis and the concomitant long delay in getting the results. Furthermore, such analysis usually results in destruction of the sample so that sample archiving is not possible. Nondestructive analysis is sometimes valuable in instances where confirmation of test results is desired long after initial sampling and reporting is made.
Generally, particulates in gas streams are analyzed by diverting a known portion of the stream to pass through a filter media onto which the particulate sample is collected. The sample is then moved to a means for analyzing the sample. Usually, the collection process needs to be halted so as to facilitate removal of the filter media.
Typically, gaseous metals entrained in the stream are collected by passing a known portion of the stream into some means for collecting such samples, such as a cold condenser or a liquid impinger where the metal sample condenses out or precipitates out. The metal sample must then be collected from the condenser or recovered from the liquid before an analysis of the sample can be made.
Devices exist for detecting the presence of certain analytes in a sample. For example, U.S. Pat. No. 5,541,057 to Bogart et al., utilizes an optically active surface to facilitate assays of biological analytes. U.S. Pat. No. 5,460,973 utilizes a combination of distillation and head space analysis to measure volatile impurities.
Other devices exist for collecting metals in the atmosphere. One such device, U.S. Pat. No. 3,940,614 to Rhodes, utilizes a high volume air sampler combined with noble-metal-coated fibrous packing. The device facilitates the collection of mercury vapor. However, no provision is made for particulate collection or analysis.
A need exists in the art for an inexpensive method and device to simultaneously measure particulate and vapor phases of metals contained in a fluid. The method and device should be adaptable to on-line operations and to installation on mobile units. The method and device should also provide for archive sampling.